I will check the Standard of Perfection for you and let you know. I want to say slate color because I used to raise bantam Ameraucanas from Little Ameraucana Mom's lines. (She would be the local expert) If you are planning on showing yours in 4-H you would probably list them under "All other breeds".
Hatchery Ameraucanas are usually bred for the colorful eggs and not for a breed standard. Most hatcheries call them Easter Eggers now, I believe, and that certainly makes it easier to explain.
There is a lot of argument about Easter Eggers and Ameraucanas. Most people want to label any non-standard color Ameraucana an Easter Egger. I disagree: If I let all my varieties of Wyandottes breed together until I was getting a rainbow of colors they would still be Wyandottes. The breed doesn't change just because of the color of the feathers.
"Easter Egger" is also used to describe a bird that lays a colored egg (green, pink, blue) that doesn't look like a typical EE.
I guess what I am saying is that if you want to get pure, bred-to-the-standard Ameraucanas to show, you need to find a breeder. But if you are wanting beautiful, colorful chickens that lay lovely colored eggs you can't beat a hatchery EE.
Personally, I like both.
I keep certain breeds that we show and then I have select chickens that I keep for my laying flock. I love a mixed basket of eggs!